Ah Ha! Thanks to w2ibc's howto on ndiswrapper, I think I've found the problem. I tried modinfo ndiswrapper, and got a "could not find module ndiswrapper error." According to the howto, the ndiswrapper module file should be: /lib/modules/18.104.22.168/misc/ndiswrapper.ko
That file does not exist on my computer! I checked the ndiswrapper package and it is only 25KB in size. By comparison, the ndiswrapper source tar.gz is 194.4KB in size! I'm thinking something is wrong with the package. Surely the source doesn't go from 194.4 to 25 KB in the packaging process.